Generally, the widely-used peripheral input device of a computer system includes for example a mouse, a keyboard, a trackball, or the like. Through the keyboard, characters or symbols can be inputted into the computer system directly. As a consequence, most users and most manufacturers of input devices pay much attention to the development of keyboards. As known, a keyboard with scissors-type connecting elements is one of the widely-used keyboards.
A keyboard with scissors-type connecting elements will be illustrated as follows. For succinctness, only one key structure is shown in the drawing. FIG. 1 is a schematic exploded view illustrating a key structure of conventional keyboard. As shown in FIG. 1, the conventional key structure 1 comprises a keycap 11, a scissors-type connecting element 12, a rubbery elastomer 13, a membrane switch circuit member 14 and a base plate 15. The keycap 11, the scissors-type connecting element 12, the rubbery elastomer 13 and the membrane switch circuit member 14 are supported by the base plate 15. The scissors-type connecting element 12 is used for connecting the base plate 15 and the keycap 11.
The membrane switch circuit member 14 comprises plural key intersections (not shown). When one of the plural key intersections is triggered, a corresponding key signal is generated. The rubbery elastomer 13 is disposed on the membrane switch circuit member 14. Each rubbery elastomer 13 is aligned with a corresponding key intersection. When the rubbery elastomer 13 is depressed, the rubbery elastomer 13 is subjected to deformation to push the corresponding key intersection of the membrane switch circuit member 14. Consequently, the corresponding key signal is generated.
The scissors-type connecting element 12 is arranged between the base plate 15 and the keycap 11, and the base plate 15 and the keycap 11 are connected with each other through the scissors-type connecting element 12. The scissors-type connecting element 12 comprises a first frame 121 and a second frame 122. A first end of the first frame 121 is connected with the keycap 11. A second end of the first frame 121 is connected with the base plate 15. The rubbery elastomer 13 is enclosed by the scissors-type connecting element 12. The first frame 121 comprises a rotary shaft 1211. The rotary shaft 1211 is disposed on a sidewall of the first frame 121. The second frame 122 has a pivotal hole 1221 corresponding to the rotary shaft 1211. After the rotary shaft 1211 is inserted into the pivotal hole 1221, the first frame 121 and the second frame 122 are combined together. Consequently, first frame 121 can be swung relative to the second frame 122, and the keycap 11 can be moved upwardly or downwardly in a stable manner.
The operations of the conventional key structure 1 in response to the depressing action of the user will be illustrated as follows. Please refer to FIG. 1 again. When the keycap 11 is depressed, the keycap 11 is moved downwardly to push the scissors-type connecting element 12 in response to the depressing force. As the keycap 11 is moved downwardly relative to the base plate 15, the keycap 11 pushes the corresponding rubbery elastomer 13. At the same time, the rubbery elastomer 13 is subjected to deformation to push the membrane switch circuit member 14 and trigger the corresponding key intersection of the membrane switch circuit member 14. Consequently, the membrane switch circuit member 14 generates a corresponding key signal. When the keycap 11 is no longer depressed by the user, no external force is applied to the keycap 11 and the rubbery elastomer 13 is no longer pushed by the keycap 11. In response to the elasticity of the rubbery elastomer 13, the rubbery elastomer 13 is restored to its original shape to provide an upward elastic restoring force. Consequently, the keycap 11 is returned to its original position where it is not depressed.
However, the conventional key structure 1 still has some drawbacks. For allowing the scissors-type connecting element 12 to be stably swung, the sizes of the rotary shaft 1211 and the pivotal hole 1221 should be accurately designed and produced. If the production tolerances of the rotary shaft 1211 and the pivotal hole 1221 are too large, the scissors-type connecting element 12 is suffered from a rocking problem. Because of the rocking problem, the movement of the keycap 11 is unstable.
Therefore, there is a need of providing a key structure with enhanced depressing stability.